1. Field of the Invention
This invention relates to an improvement in a cover for use with bound sheets to form a booklet, and in one aspect to an improved cover construction for use in forming a binding cover for sheets which are bound together with a length of pressure-sensitive adhesive tape.
2. Description of the Prior Art
Paper covers have been used for containing papers as in a file and have been used for binding sheets together. Such covers find utility with various binding systems including the use of pull-out resilient side clips which hold the cover and the marginal edges of the sheets together. Other covers have permanent tangs and eyelets. Some are formed with an accordion fold to bind the sheets together by the metal tangs. Some covers bind the sheets with "ACCO" metal fasteners at one end on the inside of the front or back cover. Other covers have a deposit of hot melt adhesive at the spine to secure pages or signatures in the cover.
All of these covers have described a system where, when the pages are bound together, the pages or sheets are bound in such a way that they cannot lie flat when the cover is open and the pages are being reviewed. This is perhaps less true with the hot melt bindings but the sheets still do not lie flat when the cover is opened.
There are also binders or covers with reinforcing at the folded edge to extend the life of the files and to prevent the same from tearing out along the crease or fold. There is in the prior art, however, no suggestion that a pamphlet or sheet binding cover should have a protective coating on the inner surface of the cover along the central fold line to permit controlled adhesion of the binding tape, wherein a pressure-sensitive adhesive binding tape is used to bind a plurality of sheets together. Such a binding is afforded wherein the sheets are shingled along one edge and the pressure-sensitive adhesive tape is applied to the shingled paper edges along one edge of the tape with the other edge of the tape adhered to the cover adjacent the fold line. A document bound in this manner thus has all of the pager secured to one another by virture of the pressure-sensitive adhesive tape being applied to the edges of the sheets and the bound sheets are secured to the cover by the same adhesive tape being applied to the inside of the back cover.
A cover which is formed only of paper is not suitable. Sometimes it is necessary or desirable to remove the bound pages from the cover. This results because of misalignment of the pages with respect to the cover when binding the same, or, it may be desirable to make changes in the bound pages and it is prudent and economical to save the covers for reuse if possible. When the cover stock is paper the pressure-sensitive adhesive on the binding tape will adhere to the paper stock. Attempts to remove the tape will cause the paper stock to delaminate or tear before the tape adhesive is released or peeled from the paper.
Thus, the present invention is directed at a paper cover stock which is designed such that a binding tape will adhere adequately to the cover, but upon demand, can be peeled from the cover without causing a delamination of the material of the cover stock. Thus, the present invention has as one object the provision of a binding cover which is adapted for use with a tape binding system for binding sheets together and securing the sheets in the cover. The cover of the present invention is so designed that the tape will hold the bound pages in the cover and will restrict displacement under normal use conditions.